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HCG - Making the Diagnosis of Pregnancy

A pregnancy should be documented as early as possible. This is important, because appropriate care and precautions can then be taken at an early stage.

The most sensitive, accurate and reliable pregnancy test is a blood test for the presence of beta HCG (human chorionic gonadotropin), often just called "beta". The HCG is produced by the embryo, and is the embryo's signal to the mother that pregnancy has occurred.

HCG is a very interesting molecule. It is unusual because it is produced only by the trophoblastic cells of the embryo ( these cells are the ones which nourish the embryo and later develop into the placenta. ) This means that if the HCG is negative , this confirms you are not pregnant. ( Men will always have a negative HCG result).

Modern urine pregnancy kits (using monoclonal antibody technology ) are now quite sensitive and can detect a pregnancy as early as 1 to 2 days after missing a period (at a blood HCG level of about 50 to 100 mIU/ml). The benefit of urine pregnancy test kits is that they are less expensive; and testing can be done at home by the patient herself. However, instructions need to be followed carefully, and errors in interpreting the test results are not uncommon. These errors could occur if the urine is too dilute; or if the test is not done properly; or if there is a urinary tract infection exists.

The post IVF 2ww is full of suspense and anxiety; and women want to know how soon they can do a urine pregnancy test after the transfer to find out if the cycle has been successful or not. Many will start testing 5 days after the transfer . However, you need to remember the limitations of the urine tests which can create problems if you test too early,

1. Even if you are pregnant, the urine test may not be positive, because the HCG levels in the urine are often very low at this time. This is called a false negative, and can depress you.
2. Even if you are not pregnant, the urine test may be positive, because of the HCG present in your body as a result of the HCG trigger shot given before egg collection. This is called a false positive, and can create false hope.

It's best to be patient - I know this waiting can be hard , but there's little choice !

Here's a simple trick to remember. If your urine test is positive, this is usually a good sign. It's a good idea to re-test the next day , at which time the test result line should become darker. This is very reassuring and strongly suggests you are pregnant.

The major advantage of blood tests is the fact that they measure the actual level of the HCG in the blood - and this factor can be very helpful in managing pregnancy problems, if they occur. You can often self-order them yourself, as sites such as www.mymedlab.com !

Beta HCG levels vary according to the gestational age. In a non-pregnant woman, they are less than 10 mIU/ml. They are typically about 100 mIU/ml 14 days after ovulation ( DPO) in a healthy singleton pregnancy.

A lot of women who have done IVF get confused when reading their HCG results ! The reason for this confusion is that they are not sure how to date their pregnancy. Shouldn't the pregnancy start from the day of the embryo transfer ? Yes, this is logical, but in real life, pregnancies are dated from the first day of the last menstrual period ( LMP). This is called the menstrual age, and is 2 weeks more than the age as calculated from DPO ( or the date of egg collection). Note that the HCG level is typically about 100 mIU/ml or more at 14 DPO . 14 DPO is considered to be 4 weeks pregnant , as measured from the LMP ( menstrual age).

As one would expect, the levels are higher in a multiple pregnancy because there is more placental tissue in a multiple pregnancy.

While a single level provides useful information , serial measurements are much more useful. HCG levels should double every 48- 72 hours in a healthy pregnancy. If the HCG levels drop, this confirms the pregnancy is miscarrying. Nothing can be done to save it . If the levels don't double as expected, this suggests that the pregnancy is unhealthy. Possibilities include a non-viable intrauterine pregnancy which will miscarry; or an ectopic pregnancy. If the beta HCG level is more than 1000 mIU/ml, and the doctor cannot see a pregnancy sac in the uterine cavity on vaginal ultrasound scan, then it's possible you have an ectopic pregnancy.

To get maximal information from a HCG level, remember that it needs to be interpreted in conjunction with your ultrasound scan results. You can see an atlas of what ultrasound scans during early pregnancy looks like here. However, there's no point in doing an ultrasound scan if your HCG level is less than 1000 mIU/ml. At such a low level, the sac is likely to be so small that the ultrasound scan will not be able to pick up anything

As the embryo grows rapidly, HCG levels normally double every 2 to 3 days. Thus, one reliable sign of a healthy pregnancy is the fact that the HCG levels are increasing rapidly, and often doctors may need to do 2 HCG levels 3 days apart in order to determine the viability of the pregnancy. A rising HCG level is reassuring.

 

Problems with HCG testing can occur if you have earlier been given HCG (human chorionic gonadotropin) injections for inducing ovulation. Normally, this exogenous HCG is excreted by the body in 10 days; but sometimes it can linger on. This is why, if the HCG level is very low, the test may need to be repeated, to confirm that the level is increasing.

What are "biochemical pregnancies" ?

These are pregnancies in which the HCG test is positive after the period has been missed; the levels increase, but are still low; and no pregnancy is ever documented on ultrasound. Biochemical pregnancies are often seen after IVF and GIFT. While they are not clinical pregnancies, they are of useful prognostic information, because they may mean that your chance of getting pregnant in a future cycle are good.

One drawback with the HCG test is that a positive HCG simply means a pregnancy is present in the body - it does not provide any information about the location of this pregnancy, which may be tubal or ectopic.

During the very early pregnancy, HCG levels are the only way of monitoring the pregnancy. HCG levels which do not increase as rapidly as they should may mean that there is a problem with the pregnancy - the embryo may miscarry because it is unhealthy; or the pregnancy could be an ectopic pregnancy. Differentiating between the two conditions is obviously important, and this is where vaginal ultrasound plays a key role.

Remember that the HCG is produced by the placenta, and not the embryo. This means that the HCG levels may continue to rise even if you have a non-viable pregnancy ( also known as an anembryonic pregnancy or missed abortion).

After 7 weeks, HCG levels are of little use in monitoring the health of the pregnancy. After this time, ultrasound scans are much more useful, as they allow us to directly see the fetus.

What if you have missed your periods and your HCG test is negative ?

This means that the reason you missed your periods is because you did not ovulate. This is called anovulation. Your doctor may need to induce a period for you using medicines such as progestins or birth control pills.

Games doctors play with HCG levels !

Many IVF doctors are very creative in manipulating the HCG results and interpreting them, because they want to inflate their success rates ! How do they fool their patients ?

  1. They give HCG injections during the luteal phase, after the embryo transfer, claiming this is for "luteal phase support". This HCG is then detected in the blood when doing the HCG blood test ( or in the urine, when doing a pregnancy test). Since the HCG test is positive, they then proudly proclaim that the patient is pregnant and that their treatment was successful. The cruel tragedy is that this just creates false hope and patients are on top of the world for a few days ! To make a bad situation even worse, they continue giving the HCG injections to "support the pregnancy". This means that the HCG levels remain positive for another few days. However , because the patient is not really pregnant, the levels soon drop. The doctor then claims that the IVF pregnancy miscarried because of "bad luck" and that the patient's best option is to try again. Patients feel that since they did get pregnant, this is a good IVF doctor - and they keep on doing IVF treatment cycles with him repeatedly.
  2. They are very liberal with interpreting what a positive HCG level is ! Technically, a level of less than 10 mIU/ml is negative. This means that anything more than 10 can be considered to be positive. Thus, when patients get levels of 14 or 16, they proudly declare that the IVF was successful and that the patient is pregnant. In reality, in a healthy pregnancy, the levels should be at least more than 30 mIU/ml 14 days after the transfer ( typically, they should be abut 100 mIU/ml or more at this time).

It's quite easy for doctors to "game the system" - and the sad truth is that some doctors will do so ! That's why it's so important for patients to be well informed !

Need help in interpreting your HCG results ?

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